Laser-assisted guidewire having a variable stiffness shaft

ABSTRACT

Embodiments of the present invention comprise a fiber optic guidewire having a hypotube with a plurality of openings that provide variable stiffness and tracking characteristics between at least one proximal segment and one distal segment of the guidewire. In some embodiments, the guidewire further comprises a mandrel disposed within the hypotube, the mandrel cooperating with the optical fibers to permit the distal end of the hypotube to be shaped as desired by a user. Methods of manufacturing and using the guidewire are also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of commonly assigned,co-pending U.S. application Ser. No. 15/061,594, filed Mar. 4, 2016,which is a divisional of U.S. patent application Ser. No. 13/737,573,filed Jan. 9, 2013, now U.S. Pat. No. 9,283,039, which is a divisionalof U.S. patent application Ser. No. 11/696,618, filed Apr. 4, 2007, nowU.S. Pat. No. 8,414,568, which claims the benefit of U.S. ProvisionalPatent Application Ser. No. 60/788,891, filed Apr. 4, 2006. Thisapplication is also related to U.S. Pat. Nos. 5,514,128 and 5,643,251.The entire content of each of these documents is incorporated herein byreference for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates generally to improved devices and methodsfor the delivery of laser energy within a mammalian subject and, morespecifically, to fiber optic guidewires and methods of using same.

Angioplasty and atherectomy are therapeutic medical procedures in whicha catheter or the like is inserted into a blood vessel to increase bloodflow. In such procedures, a steerable guidewire of relatively smalldiameter is typically inserted into the patient's blood vessel and movedinto proper position past the obstruction. Then a larger treatingcatheter, as some examples only, a balloon catheter or a laser catheter,is advanced along the guidewire until the catheter is in properposition. The guidewire makes it easier to position the catheterrelative to the target site. The catheter is then operated to accomplishits intended purposes. When the catheter and guidewire are withdrawn,the previously obstructed area remains dilated, and blood flow in thetarget area is increased.

Catheters containing optical fibers transmit energy to irradiateinternal parts of the body for diagnostic and therapeutic purposes.There are many medical applications in which it is desirable to deliverenergy, such as laser energy, through an optical fiber or similarwaveguide device disposed in a body cavity for treatment or diagnosis.These include, among others, the ablation of tissue such as plaque andtumors, the destruction of calculi, and the heating of bleeding vesselsfor coagulation. The lasers used may produce either pulsed orcontinuous-wave light of wavelengths ranging from the ultra-violet tothe infra-red.

Although a laser catheter can ablate the occlusion, its relatively largediameter sometimes prohibits adequate positioning within the vessel toperform the ablation. Moreover, in some situations, such as with chronictotal occlusions, the shape and nature of the vascular occlusion may notpermit a guidewire to be positioned so that a laser catheter can beinserted to perform the ablation.

Current mechanical guidewires are limited to mechanical forcestransferred to the tip of the device through the shaft in order tocreate dissections within the vascular occlusions. These mechanicalguidewires often cannot cross or penetrate lesions that are often highlycalcified in nature, and they do not employ laser energy to facilitatethe crossing of vascular lesions. Thus, an unmet need remains for aguidewire system that can consistently penetrate and cross chronic totalocclusions within the mammalian vasculature with suitable stiffness andtorque characteristics.

Embodiments of the present invention provide solutions to at least someof these problems.

BRIEF SUMMARY OF THE INVENTION

The unmet need is met in the present invention by providing a fiberoptic guidewire with a hypotube having a proximal end and a distal end,an adhesive plug within the distal end of the hypotube having a distalface substantially flush with the distal end termination of thehypotube, and a plurality of optical fibers disposed within thehypotube, wherein the optical fibers extend through the adhesive plugand have a distal face terminating at the distal face of the adhesiveplug. The adhesive plug surrounds the optical fibers and fixes thefibers within the distal end of the hypotube. The hypotube is alsocomprised of at least one distal segment having an outer surface with aplurality of openings that provides variable stiffness and trackingcharacteristics between at least one proximal segment and one distalsegment of the guidewire. In some embodiments, the guidewire furthercomprises a mandrel disposed within the hypotube, with a distal endterminating at the distal end of the hypotube, the mandrel cooperatingwith the optical fibers to permit the distal end of the hypotube to beshaped as desired by a user.

Embodiments of the invention may be maneuvered and positioned in thevasculature like a conventional guidewire using a torque transmittingdevice. Laser energy from an energy source at the proximal end of theguidewire may be conveyed to the intravascular target area by theoptical fibers to ablate an obstruction. Once the guidewire has ablateda passage in the obstruction, its proximal end may be severed distal tothe proximal coupler. The fail section and torque device may then beslid off or removed from the severed end, leaving a distal hypotube within the patient. A larger treatment catheter may then be slid over theremaining guidewire to continue the ablation procedure. Additionally,other treatment catheters may be freely loaded on and off the guidewireas needed.

Guidewire systems and method provided herein are well suited for use intreating chronic total occlusions with laser energy. Advantageously,these systems provide handling characteristics of a guidewire andablation characteristics of a laser delivery device. Embodimentsdisclosed herein provide efficient and effective solutions foraddressing coronary and peripheral chronic total occlusions that may notbe crossable or penetrable by standard guidewire modalities. Thesesolutions allow physicians and other system operators to cross vascularlesions in a safe, reliable, and consistent manner.

In one aspect, embodiments of the present invention provide fiber opticguidewire. The guidewire can include, for example, a hypotube having aproximal end and a distal end, an adhesive plug within the distal end ofthe hypotube and having a distal face substantially flush with thedistal end termination of the hypotube, and a plurality of opticalfibers disposed within the hypotube. The optical fibers may extendthrough the adhesive plug and have a distal face terminatingsubstantially at the distal face of the adhesive plug. The adhesive plugcan surround the optical fibers and bond the fibers within the distalend of the hypotube. The hypotube can include at least one distalsegment having an outer surface with a plurality of openings providingvariable stiffness and tracking characteristics between at least oneproximal segment and one distal segment of the guidewire. In some cases,the guidewire includes a mandrel disposed within the hypotube. Themandrel can have a distal end that terminates substantially at thedistal end of the hypotube. The mandrel can cooperate with the opticalfibers to permit the distal end of the hypotube to be shaped as desiredby a user. In some cases, the hypotube can include at least one proximalportion having a first stiffness and at least one a distal portionhaving a second stiffness less than the first stiffness. The guidewiremay also include a proximal coupler. The hypotube may include stainlesssteel, Nitinol, or both. In some cases, the guidewire comprises abending stiffness of about 0.004 grams at or near a location about 1 cmfrom the distal end of the hypotube corresponding to a deflectiondistance of about 0.200″ in a 1″ three point bend stiffness test.

In another aspect, embodiments of the present invention include a fiberoptic guidewire. The guidewire can include, for example, a hypotubehaving a proximal end, a distal end, and a segment or wall having anouter surface with a plurality of openings providing variable stiffnessand tracking characteristics to the hypotube. The guidewire may alsoinclude two or more optical fibers disposed within the hypotube, and anadhesive plug within the hypotube that surrounds the optical fibers andbonds them to the hypotube. In some cases, the adhesive plug extendsradially into at least one of the outer surface openings of thehypotube. The guidewire may also include a mandrel disposed within thehypotube. The hypotube can include at least one proximal portion havinga first stiffness and at least one distal portion having a secondstiffness less than the first stiffness. In some cases, the hypotube hasa flexibility that increases as a linear function of a position alongthe hypotube extending from a proximal location to a distal location. Insome cases, the hypotube has a flexibility that increases as a smoothand continuous function of a position along the hypotube extending froma proximal location to a distal location. The hypotube may include aplurality of hoops such that each hoop is coupled with an adjacent hoopvia a brace. In some cases, the length of each hoop is constant. In somecases, the length of each brace is constant. Optionally, the length ofeach hoop can be smaller than the length of the proximal adjacent hoop.In some cases, the adhesive plug is disposed toward the distal end ofthe hypotube, and the guidewire further includes a second adhesive plugwithin the hypotube disposed between the distal and proximal ends of thehypotube. The second adhesive plug can surround the optical fibers andbond them to the hypotube. The guidewire may also include a thirdadhesive plug within the hypotube disposed toward the proximal end ofthe hypotube. The third adhesive plug can surround the optical fibersand bond them to the hypotube.

In another aspect, embodiments of the present invention provide a methodof manufacturing a guidewire. The method can include, for example,providing a hypotube having a proximal end and a distal end. Thehypotube can have a plurality of apertures disposed in a wall of thehypotube between the proximal end and the distal end. The method canalso include placing two or more optical fibers at least partiallywithin the hypotube, and introducing an adhesive material into thehypotube. The method may include allowing the material to wick along theoptical fibers and into at least one of the plurality of apertures ofthe wall of the hypotube, such that the adhesive material forms anadhesive plug that fixes the optical fibers relative to the hypotube. Insome cases, the method includes inserting a mandrel at least partiallywithin the hypotube. In some cases, the guidewire includes at least oneproximal portion having a first stiffness and at least one a distalportion having a second stiffness less than the first stiffness.

For a fuller understanding of the nature and advantages of the presentinvention, reference should be had to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a side view of one embodiment of the invention.

FIG. 2 is a drawing of cut-away side view of a hypotube of oneembodiment of the invention comprising a mandrel.

FIG. 3 is a drawing of the distal lip of the guidewire.

FIG. 4 is a drawing of the distal tip of one embodiment of theguidewire.

FIG. 5 is a side view of a hypotube.

FIGS. 6A, 6B, and 7 are drawings of one embodiment of a hypotube withsegments of similar or differing slot widths.

FIGS. 8, 9A, and 9B are drawings of an embodiments of a hypotube of theinvention containing spiraled slots.

FIGS. 10A, 10B, and 10C are a drawings of axial cross-sections of ahypotube of an embodiment of the invention comprising a mandrel, perFIGS. 1 and 2.

FIG. 11 is a drawing of a side cross-sectional view of an exchange leadsegment of the invention.

FIG. 12 shows a portion of a fiber optical guidewire according toembodiments of the present invention.

FIGS. 13 and 14 show fiber optical guidewires according to embodimentsof the present invention.

FIGS. 15, 16, 17, 18, and 19 show graphs depicting hypotube flexibilityprofiles according to embodiments of the present invention.

FIGS. 20, 21, 22, 23, and 24 show graphs depicting hypotube stiffnessprofiles according to embodiments of the present invention.

It should be noted that the relative sizes and dimensions of elements ofthe invention are not drawn to scale and may be exaggerated fordemonstration purposes.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention encompass fiber optic guidewiresystems and methods for their use and manufacture. An exemplary fiberoptic guidewire includes a hypotube having a proximal end and a distalend, and a plurality of optical fibers disposed within the hypotube. Theoptical fibers can be anchored or secured to the hypotube with one ormore adhesive plugs. The hypotube can include apertures or grooves thatprovide variable stiffness and tracking characteristics. The fiber opticguidewire may also include a mandrel disposed within the hypotube.Guidewire embodiments disclosed herein can provide steering and torquecharacteristics that are equivalent to or exceed those observed in othercommercially available mechanical guidewires. Moreover, guidewireembodiments disclosed herein provide improved flexibility or stiffnesscharacteristics as compared to other commercially available mechanicalguidewires.

Catheter guidewires can include a distal tubular flexible portion.Optical fibers can be disposed within the tubular portion. The guidewiresystem may include radiopaque markers near or toward the distal end, orat any desired location on the system. The tubular portion or hypotubemay include openings such as slots, slits, spiral cuts, and the like, toprovide desired force transmission, torsional control, and tip shapingcapabilities, as well as variable stiffness and trackingcharacteristics, to the guidewire system. In use, the guidewire can bemaneuvered into a vascular area and laser energy can be transmittedthrough optical fibers disposed within the hypotube, toward a vascularobstruction.

Turning now to the drawings, in some embodiments, without limitation,the invention comprises a fiber optic guidewire 1 with a proximal end 3and a distal end 5. The guidewire 1 includes a tail tube 7 and ahypotube 9, with a plurality of optical fibers 11 disposedlongitudinally therein as shown, for example, in FIGS. 1 and 2. Thedevice comprising the invention may be of any suitable length A, with alength A between about 350 cm and about 390 cm preferred in someembodiments. The tail tube 7 can include plastic tubing that connects atits proximal end to a proximal coupler 33 with heat shrink 14 and strainrelief 12. The tail tube 7 can be configured to interface with thehypotube 9 over an exchange lead 15, as further illustrated in FIG. 11.The hypotube segment 9 of the guidewire 1 can be a tubular elementhaving a plurality of optical fibers 11 disposed therein from itsproximal end to its distal end. The hypotube segment 9 may be of anysuitable length B, with a preferred length of between 160 and 180 cm insome embodiments. The hypotube 9 typically has at least one flexibledistal segment 17.

In some embodiments, the plurality of optical fibers 11 disposed withinthe guidewire extend from or between its proximal end to its distal end.The optical fibers 11 can be polyimide-buffered optical fibers eachhaving a diameter of about 25 to about 75 microns, with fibers of about50 microns preferred in some embodiments. In some preferred embodiments,the invention is comprised of seven fibers 11 disposed within at leastpart of the longitudinal length of the guidewire. The number ofindividual fibers, their corresponding diameter, and their type, can beselected according to desired flexibility characteristics of thehypotube or guidewire. Fiber flexibility can be defined as the forcethat is needed to deflect a fiber through a given distance. In manycases, this amount of force is observed to increase with the fourthpower of the fiber diameter. The flexibility of a bundle of fibers canbe increased by reducing the diameter of the fibers in the bundle,because the fiber area increases with the square of the diameter. Forexample, a bundle of four fibers, each having a diameter of 100 microns,provides a fiber area equivalent to a single fiber having a diameter of200 microns. The bundle and the single fiber can deliver the same amountof light energy (due to equivalent total cross sectional areas), yet thebundle is four times as flexible as the single filter.

In manufacturing the guidewire 1, optical fibers of the selected size(s)and number are typically unspooled and stranded together in the desiredlengths. The bundled optical fibers 11 are disposed within the tail tube7, exchange lead 15, and hypotube 9. In some embodiments, at theproximal end 3 of the guidewire, the proximal ends of the optical fibers11 are connected into a proximal coupler 13. The proximal coupler 13 maythen be inserted into an energy source (not shown).

In some embodiments, at their distal ends the optical fibers 11terminate at a tip 19 at the most distal end of the guidewire. Theoptical fibers 11 can be potted in an adhesive plug 21 extendingproximally from the distal end of the hypotube for up to about 1 cm,with about 0.2 cm in some preferred embodiments. In some embodiments,optical fibers 11 can be potted at one or more locations along thelength of hypotube 9. For example, optical fibers 11 can be potted inadhesive or otherwise fixed to hypotube 9 at a distal location along thehypotube 9, at a proximal location along hypotube 9, at an intermediatelocation along hypotube 9 between the distal and proximal locations, orany desired combination thereof. Suitable potting adhesives are known tothose of ordinary skill in the art. In some cases, a potting adhesiveincludes un epoxy material. Often, an adhesive material is selected toprovide at least a certain minimum hardness characteristic, or relatedlyto provide sufficient durability so as to withstand any degradativeeffect produced by the ablative energy that travels through the fiberoptic bundle. Typically, an adhesive that has a higher hardness valuewill impart a greater degree of stiffness to the guidewire, as comparedto an adhesive with a lower hardness. Guidewire sections that containadhesive are usually less flexible than guidewire sections having noadhesive, as an adhesive plug can provide a non-deflecting or aminimally deflecting characteristic to the guidewire. In someembodiments, the distal faces of the adhesive plug 21 and the opticalfibers 11 terminate substantially co-extensively with the distal face ofthe hypotube 9, for example as shown in FIGS. 2, 3, and 4. Afterpotting, the distal end of the tip 19 may be ground and polishedaccording to methods known to those of ordinary skill in the art. Thedistal tip may be beveled to provide a less traumatic profile in someembodiments. As shown in FIG. 3, the outer diameter H of the distal tipof the hypotube can be within a range of about 0.0125″ to about 0.0145″.In some cases, outer diameter H is about 0.0135″ or about 0.014″. Theouter diameter can be inclusive of any radiopaque coatings andhydrophilic coatings disposed on the hypotube. The individual diameterof each fiber can be about 50 microns.

Optionally, the outer diameter of the distal tip can be between about0.005 and about 0.018 inches, with an outer diameter of about 0.014inches in some preferred embodiments. A distal segment 23 of theguidewire comprising the tip may be coated with or otherwise incorporatea radiopaque material, as one example only, with gold plating for adesired length F. In some cases, length F is about 3 cm. The radiopaquematerial can be incorporated into the hypotube, an adhesive plug, amandrel, or any other component of the fiber optic guidewire, at anylocation on the component. In some cases, the radiopaque material isgold, platinum, or some other fluoroscopically detectable substance. Insome embodiments, a hypotube is coated or plated with a layer of gold ofabout 1 to about 2 microns in thickness. In some embodiments, a hypotubeis coated with a layer of gold of about 3 to about 4 microns inthickness. In some embodiments, a hypotube is coated with a layer ofgold of about 5 to about 6 microns in thickness. In some embodiments, ahypotube is covered with a slippery, smooth, or lubricious material.Exemplary hydrophilic polymer coatings or materials that may be used fora hypotube covering are produced by Surmodics, Inc. of Eden Prairie,Minn.

In preferred embodiments, without limitation, at least some portion 25of the outer surface of the hypotube 9 comprises a plurality of openings27 for providing desired variations in stiffness along at least somelength of the hypotube, for example as shown in FIGS. 2 and 5. Forexample, a slotted section 25 of the hypotube 9 cart extend proximallyfrom the distal end of the catheter for a distance J, which can be about30 cm. The openings may comprise slots, slits, spirals, apertures, orother configurations suitable for these purposes. In some embodiments,the hypotube includes a material or structure in place at least some ofthe openings, whereby the material or structure is compressible andconfers flexibility to the hypotube when the guidewire is bent,deflected, or otherwise guided through the vasculature of a patient. Insome embodiments, a hypotube may include a compressible elastomer, aflexible adhesive, or a deformable plastic or other material where theaperture or opening would otherwise be located. In some cases, ahypotube may include such elements or a thin wall between hoops andbraces of the hypotube so as to impart desired flexibilitycharacteristics to the guidewire. Accordingly, the hypotube may bedevoid of openings or apertures.

The hypotube 9 may be made of metal, plastic, polymers, or anycombination thereof. In some preferred embodiments, the hypotube 9 isconstructed of stainless steel or nickel-titanium alloy, such asNitinol. The openings 27 may be formed by grinding, cutting, molding,etching, laser cutting, or other methods known to those of ordinaryskill in the art. Optionally a low-friction substance, such as PTFE or asimilar lubricant, may be applied to the exterior surface of thehypotube, along length B as shown in FIG. 1. The low friction substancecan be applied to the entire length of the hypotube, or to one or morediscrete sections of the hypotube. As shown in FIG. 5, hypotube 9 has alength I which can be within a range from about 74.58 cm to about 75.18cm. For example, length I can be about 74.88 cm.

In some embodiments, measuring longitudinally from the distal end of theguidewire, the hypotube may include a solid, unslotted surface 29 havinga length C up to about 0.3 cm. In some cases, length C can be up toabout 0.085 cm. See, for example, FIGS. 2, 4, 5 and 6A. Thereafter,continuing proximally along the guidewire 1, the hypotube 9 maycomprises slots or other suitable openings 27 or compressible elementsat predetermined intervals. The adhesive plug 21 at the distal end ofthe hypotube 9 can be formed in the unskilled portion and may be wickeddown selectively into the first few openings 27 of the hypotube 9. Theguidewire can also include a mandrel 31, as shown in FIG. 2. Mandrel 31can extend proximally from the distal end of the catheter for a distanceD. In some preferred embodiments, without limitation, distance D can bebetween about 34.92 cm and about 36.20 cm. For example, distance D canbe about 35.56 cm. The outer surface of the hypotube may be of uniformouter diameter or optionally may be tapered along its length. Forexample, a more proximal section of the hypotube may have a largerdiameter, whereas a more distal section of the hypotube may have arelatively smaller diameter. In some embodiments, a more proximalsection of the hypotube may have a larger outer diameter, whereas a moredistal section of the hypotube may have a relatively smaller outerdiameter. Similarly, in some embodiments, a more proximal section of thehypotube may have a smaller inner diameter, whereas a more distalsection of the hypotube may have a relatively larger inner diameter.

As illustrated in FIG. 6A, in some embodiments a hypotube can have alength O of about 190 cm. The hypotube includes a proximal portion,having a length C, that has no openings. Length C can be about 0.0400″.The hypotube also includes a first slotted hypotube section 26 a, asecond slotted hypotube section 26 b, and a third slotted hypotubesection 26 c. The first slotted hypotube section 26 a can have a distalend which is disposed at a length C from the distal tip of the hypotube,and a proximal end which is disposed at a distance L from the distal tipof the hypotube. Distance L can have a length of about 1 cm. In thefirst slotted hypotube section 26 a, each of the hoops 640 of thehypotube have a first hoop length HL.sub.1. The second slotted hypotubesection 26 b can have a distal end which is disposed at a length L fromthe distal tip of the hypotube, and a proximal end which is disposed ata distance M from the distal tip of the hypotube. Distance M can have alength of about 15 cm. In the second slotted hypotube section 26 b, eachof the hoops 640 of the hypotube have a second hoop length HL.sub.2. Thethird slotted hypotube section 26 c can have a distal end which isdisposed at a length M from the distal tip of the hypotube, and aproximal end which indisposed at a distance N from the distal tip of thehypotube. Distance N can have a length of about 30 cm. In the thirdslotted hypotube section 26 c, each of the hoops 640 of the hypotubehave a third hoop length HL.sub.3. As shown in FIG. 6A, HL1 is smallerthan HL2, and HL2 is smaller than HL3. A hypotube having such aconfiguration can provide a flexibility profile similar to the one shownin FIG. 16, where the flexibility of the hypotube changes as adiscontinuous stepwise function at locations along the length of thehypotube.

FIG. 6B shows a hypotube configuration where the hoop length 942 of eachsuccessive hoop 940 is shorter than the hoop length of the neighboringproximal hoop, and each brace 950 has the same brace length 952. Ahypotube having such a configuration can provide a flexibility profilesimilar to the one shown in FIG. 17, where the flexibility of thehypotube changes as a linear function at locations along the length ofthe hypotube. Optionally, a hypotube can have a configuration where thehoop length 942 of each successive hoop is constant, and the bracelength 952 of each successive brace 950 is longer that the brace lengthof the neighboring proximal brace. Such a configuration can also providea flexibility profile similar to the one shown in FIG. 17. FIG. 7 showsan exemplary hypotube configuration according to embodiments of thepresent invention.

In some embodiments, without limitation, a slotted segment of hypotubemay extend proximally from the distal end of the guidewire for adistance up to about 60 cm. In some embodiments, the slotted segment ofthe hypotube comprises at least 2 slotted segments of differing spatialseparation of slots, as shown in FIGS. 8, 9A, and 9B. For example, thepitch or spacing between apertures or grooves in the hypotube can besmaller at the distal section and larger at the proximal section. Insome embodiments, the pitch at a more distal section of the hypotube isabout 0.012″ and the pitch at a more proximal section of the hypotube isabout 0.072″. The spacing of the pitch may change in a linear pattern inrelationship to the length of the hypotube, so that the pitch graduallybecomes larger toward the proximal end. In some cases, the spacing ofthe pitch may change in a non-linear but otherwise smooth and continuousrelationship to the length of the hypotube, again so that the pitchgradually becomes larger toward the proximal end. In some cases,discrete sections of the hypotube provide apertures or grooves at aconstant pitch, and the hypotube includes one or more sections ofvarying pitch. The hypotube may also comprise a spiral of uniform ornonuniform pitch, for example as shown in FIGS. 8, 9A, and 9B. Ahypotube having a spiral pitch configuration as shown in FIG. 9B, forexample, by be constructed by cutting a spiral groove in a lobularmember. The width of the spiral groove may vary along the length of thetube. For example, the width of the groove may be greater at the distalend of the tube, and narrower at the proximal end of the tube.Optionally, the spiral cut can be made in the hypotube so as to providea constant pitch or a variable pitch along the length of the hypotube.In some embodiments, a hypotube comprises a ribbon of material having aconstant width. In some embodiments, a hypotube comprises a ribbon ofmaterial having a width that continuously and smoothly increases towardthe proximal end of the hypotube. Similarly, in some embodiments ahypotube comprises a ribbon of material having discrete sections wherethe width of each successive section is larger than the width of theadjacent distal section. In some embodiments such a hypotube can have anouter diameter of about 0.014″ and an inner diameter of about 0.0085″.As shown in FIG. 9A, a distal portion of the hypotube can have a sectionwhere the groove or aperture pitch is constant, the section having aproximal end that is disposed at a distance P from the distal end of thehypotube. Here, the pitch is about 0.012″. Distance P can have a lengthwithin a range from about 1.10″ to 1.26″. For example, distance P can beabout 1.18″. The hypotube can also have another section where the pitchvaries at distances along the length of the hypotube. For example, adistal end of a variable pitch section can be at a distance P from thedistal end of the hypotube, and extend to a distance Q from the distalend of the hypotube. Distance Q can have a length within a range fromabout 11.4″ to about 12.2″. For example, distance Q can he about 11.8″.The hypotube can have a length R within a range from about 58.5 to about59.5. For example, length R can be about 59″. The slot width, or span ofthe aperture, can be within a range from about 0.001 inch to about 0.002inch. In some embodiments, a hypotube having a spiral cut, groove, oraperture can also have one or more struts or braces spanning the cut oraperture (similar to the braces shown in FIG. 12) so as to provide alongitudinal connection between neighboring loops or hoops of the spiralhypotube. A strut can have a width of, for example, 0.011″. Struts canbe disposed along a spiral hypotube at every 450 degrees. The hypotubemay include other strut width and spacing configurations so as toprovide a desired flexibility profile. In general, a spiral hypotubehaving struts placed at every 50 degrees is less flexible than a spiralhypotube having struts placed at every 450 degrees. Similarly, a struthaving a width of 0.009″ will impart more flexibility than a struthaving a width of 0.011″. As shown in FIG. 9B, a hypotube can have afirst section P.sub.1 with a first spiral pitch, a second sectionP.sub.2 with a second spiral pitch, and a third section P.sub.3 with athird spiral pitch.

In some embodiments, without limitation, the optical fibers are disposedwithin at least a portion of the hypotube 9 around a core mandrel 31,for example as shown in FIG. 2. The mandrel 31 may extend within thehypotube 9 proximally from the distal end for a length D. In someembodiments, length D can be between about 30 cm and about 40 cm. Forexample, length D can be about 35.5 cm. The mandrel 31 may be tapered,with its most distal end or portion flattened and rectangular incross-section for a distance E. In some embodiments, distance E isbetween 0.1 and 2 cm. For example, distance E can be about 1.5. FIG. 10Ashows a cross section along the hypotube at the location indicated inFIG. 2, where the optical fibers 11 are shown in a circumferentialarrangement around mandrel 31. The cross-section of mandrel 31 is shownas having two opposing flattened sides and two opposing circular orarcuate sides. FIG. 10B show's a cross section along the hypotube at thelocation indicated in FIG. 2, where the optical fibers 11 are shown in acircumferential arrangement around mandrel 31. The cross-section ofmandrel 31 is shown as a circle. FIG. 10C shows a cross section alongthe hypotube at the location indicated in FIG. 1, where the opticalfibers 11 are shown in a circumferential arrangement within thehypotube, without an inner mandrel. In some embodiments, the distal endof the flattened portion of the mandrel is substantially central to andcoterminal with the terminal face of the hypotube. The distal end of themandrel can be mounted in the adhesive plug 21 and provide shapeabilityand durability to the guidewire. The adhesive plug can fix the distalends of optical fiber bundle and the mandrel in place within thehypotube.

The mandrel may have an intermediate portion which tapers to theflattened distal portion. The proximal end of the mandrel, along withthe optical fibers, can be potted in another adhesive plug formed byinserting adhesive into, for example, the most proximal opening 27 inthe hypotube. In some embodiments, without limitation, the mandrel isfabricated from stainless steel or tungsten and can be either a taperedor nontapered mandrel. Its outer diameter may range from about 0.002 in.to about 0.005 in., with a length of about 1.5 cm to about 190 cm. Theflattened portion can have a rectangular cross-section and can cooperatewith the optical fibers to allow the guidewire to be shaped and reshapedto bend at a desired angle, for example as shown in FIGS. 2 and 10A.

As shown in FIG. 11, which corresponds to the location indicated in FIG.1, the proximal end of the hypotube 9 can be configured to interfacewith the tail tube 7. In some embodiments, a tubular clear exchange lead15 is disposed over the optical fibers 11 at the proximal end of thehypotube 9. The exchange lead 15 can have a length G, where length G iswithin a range from about 5 cm to about 9 cm. For example, length G canbe about 7 cm. A suitable adhesive, which will be known to those ofordinary skill in the art, can be applied to the proximal end of thehypotube 9 to pot the optical fibers 31 in place. Similarly, a suitableadhesive can be applied to the adjacent distal end of the exchange lead15, thereby joining it with the hypotube 9.

As shown in FIG. 1, some embodiments of the present invention furthercomprise a torque knob 37 disposed on the guidewire. The torque knob maybe of any suitable configuration known to those of ordinary skill in theart. The torque knob may be positioned at almost any location along theshaft of the hypotube for case of handling, torquing, and steeringduring a procedure. When the torque knob is tightened onto the hypotube,the torque knob may be rotated to apply torque to the guidewire. Thedistal end of the tail tube can interface insertably with an interiorsegment of the torque knob.

The guidewire may be advantageously used to ablate an intravascularocclusion and/or to position a catheter. As one example only, theguidewire is connected to a source of laser energy by way of proximalcoupler. The hypotube segment of the guidewire is maneuvered into thevasculature like a conventional guidewire and positioned so that thedistal tip is proximate to the target site. Energy from the laser sourceis transmitted through the optical fiber bundle to the tip, therebyablating a channel through the occlusion. Optionally, once a channel hasbeen ablated, the guidewire may be cut at or near the exchange lead, theproximal end of the guidewire and torque knob removed, and the guidewiresegment remaining in the patient may be used as a mechanical guidewireto guide a larger catheter or other device for further treatment. Theproximal end of the newly-severed optical fibers is pulled away fromexchange lead and then detached so that the fibers retract inside thehypotube. A catheter may then be placed on the proximal end of thehypotube and slid down to the point of entry over the hypotube into thepatient's body. The catheter is then introduced into the patient's bodyand slid along the hypotube until it reaches the desired target near thepartially-ablated occlusion. With this procedure, a laser catheter maybe used to ablate a larger area of the occlusion. Numerous variations ofand substitutions for the above-described method will be readilyapparent to one of ordinary skill in the art.

FIG. 12 illustrates aspects of an optical guidewire system 100 accordingto embodiments of the present invention. Optical guidewire system 100includes a hypotube 110, a bundle of optical fibers 120, and an adhesiveplug 130 that forms a joint bond where the optical fibers are fixedrelative to the hypotube arid to one another. Hypotube 110 includes analternating series of circumferentially oriented hoops 140 andlongitudinally oriented braces 150. Each hoop 140 has a hoop length 142and a hoop depth 144. Each brace 150 has a brace length 152, a bracedepth 154, and a brace width 156. As shown here, there are two bracesbetween each two neighboring hoops, and the braces are disposed onopposing sides of the hypotube. Adhesive plug 130 may includeprojections 132 that extend radially outward from a central longitudinalaxis of the hypotube. Projections 132 may be disposed between hypotubehoops 140 and braces 150. Often, a projection 132 extends radiallyoutward so as to span the full distance of hoop depth 144 and bracedepth 154.

For a typical hypotube, the presence of an adhesive plug 130 will impartgreater stiffness to a guidewire than will the absence of an adhesiveplug. Similarly, a longer hoop length 142 can impart greater flexibilitythan a shorter hoop length. A longer brace length 152 will typicallyimpart a greater flexibility than a shorter brace length. A larger bracewidth 156 can impart greater stiffness than a smaller brace width. Alarger hoop depth 144 or brace depth 154 can impart greater stiffnessthan a smaller hoop depth or smaller brace depth, respectively.Variations in hoop depth 144 and brace depth 154 can be introduce viatapering, boring, or grinding techniques that change the inner diameterand the outer diameter of the hypotube. Relatedly, techniques that varythe wall thickness of the hypotube can also vary the hoop depth andbrace depth. In some embodiments, a hypotube is constructed by placing acut 170 in the body of the hypotube, so as to form an aperture in thetube. Often, the cut will be made transverse to a central longitudinalaxis of the hypotube. A deeper cut or slot 170 can result in a smallerbrace width 156. Similarly, a more shallow cut 170 can result in alarger brace width 156. As shown here, a cut width can correspond to thebrace length 152. In some embodiments, a brace length 152 can be withina range from about 0.001 inch to about 0.002 inch. In some cases, abrace length 152 can be within a range from about 0.002 inch to about0.005 inch.

An exemplary method of forming such adhesive plugs includes placing aportion of the hypotube into a mold, pouring or injecting an adhesiveinto the mold, heating the adhesive so that it is wicked within thehypotube along the optical fibers, introducing cold air at one end ofthe mold so as to initiate setting of the adhesive. As noted above,adhesive can extend radially into spaces between the hoops and braces ofthe hypotube, and thus provide an anchor to prevent the optical fibers,and optionally the mandrel, from slipping longitudinally within thehypotube.

In some embodiments, an optical guidewire system may include a pluralityof adhesive plugs. The adhesive plugs can lie spaced at discretelocations along the length of the hypotube. For example, an opticalguidewire system 100 may include one more sections X where there is anadhesive plug, and one or more sections Y where there is not an adhesiveplug. At sections X, where there is an adhesive plug, the optical fibersare potted within the hypotube to create a composite structure. Thus,the individual fibers of the bundle are restricted from moving freelywithin the hypotube, and from moving relative to each other or relativeto the hypotube. Such movement is also inhibited even when the guidewiresystem is bent or deflected. If the guidewire system includes a mandrel,the fibers may be bonded with the mandrel as well. At sections Y, wherethere is no adhesive plug, the individual fibers of the bundle can movefreely within the hypotube, and can move relative to each other andrelative to the hypotube. This allows the hypotube and each of theindividual fibers to operate or function independently when theguidewire system is snaked through a tortuous vessel or lumen. Suchfreedom of movement can impart a component of flexibility to theguidewire system.

In an exemplary embodiment, as shown in FIG. 13, a guidewire system 200can include a hypotube 210 with a bundle of optical fibers 220 and amandrel 240 disposed therein. The optical fibers and mandrel are pottedwithin the hypotube at the distal end of the hypotube with an adhesiveplug 230. The cross section of the mandrel can provide two opposing flatsides and two opposing arcuate sides, similar to a flattened rod. Insome embodiments, as shown in FIG. 14, a guidewire system 300 includes ahypotube 310 having a length of about 190 cm with a bundle of opticalfibers 320 and a mandrel 340 disposed therein. The optical fibers arepotted within the hypotube at the distal end of the hypotube with afirst adhesive plug 330 a, at an intermediate section locatedapproximately 3 cm from the distal end of the hypotube with a secondadhesive plug 330 b, and at the proximal end of the hypotube, or at theproximal end of a proximal slotted section of the hypotube,approximately 30 cm from the distal end of the hypotube with a thirdadhesive plug 330 c. The third adhesive plug can be disposed Each ofthese three bond joints can have a length within a range from about 3 cmto about 4 cm. The distal end of the core mandrel may be disposed at anydesired location along the length of the hypotube. For example, thedistal end of the mandrel may be disposed at or near the intermediatebond joint. In some cases, the system may not include a mandrel disposedon the interior of the fiber bundle.

Often, a mandrel will he constructed of a material that is more densethan the hypotube. A mandrel can operate as a security feature to theguidewire system so that if the hypotube breaks, the mandrel provides anadditional structure within the system, thus serving to maintain orpreserve the structural integrity of the system. Moreover, a mandrel canimpart an additional degree or variability of stiffness to the guidewiresystem, depending on the material used to manufacture the mandrel andthe configuration of the mandrel. The mandrel can also serve as avisualization feature, for example by incorporating radiopaque elements.In some embodiments, a mandrel can have a constant diameter or crosssection along the length of the mandrel. In some embodiments, a mandrelcan have a diameter or cross section that varies along the length of themandrel. The diameter or cross-section can vary in a stepwise fashion orin a linear fashion along the length of the mandrel, for example. Suchmandrel configurations can impart desirable flexibility profileconfigurations to a guidewire. In some cases, a variable stiffnessmandrel can be combined with a variable stiffness hypotube. In somecases, a variable stiffness mandrel can be combined with a constantstiffness hypotube.

As illustrated in FIG. 12, adjacent hypotube hoops 140 can be separatedby intervening braces 150. In some embodiments of the invention, eachhoop has the same hoop length 142 and each brace has the same bracelength 152. Such hypotube construction can provide a flexibility profileas shown in FIG. 15, where the flexibility FL of the hypotube isconstant at each location HT along the length of the hypotube, from theproximal end PR to the distal end D1. Often, flexibility can beinversely related to bending stiffness. Optionally, the hypotube can beconstructed so that it provides a first section where each hoop has afirst hoop length 142 and each brace a first brace length 152 and asecond section where each hoop has a second hoop length 142 and eachbrace a second brace length 152, such that the first and second hooplengths are different and the first and second brace lengths aredifferent. A hypotube having this configuration can provide aflexibility profile as shown in FIG. 16, where the flexibility FL of thehypotube increases as a discontinuous stepwise function at locations HTalong the length of the hypotube, from the proximal end PR to the distalend D1. Spiral hypotubes having discrete stepped pitch regions, such asthose shown in FIG. 9B, can also provide such a flexibility profile.Similarly, hypotubes having discrete stepped cut width regions canprovide such flexibility profiles.

In another embodiment, each hoop has the same hoop length 142, and eachbrace has a brace length 152 that is longer than the brace length of theneighboring proximal brace. Hypotube configurations such as this canprovide a flexibility profile as shown in FIG. 17, 18, or 19 dependingon the degree to which brace length increases along the hypotube. Forexample, the increasing change in brace length may impart a flexibilityprofile where the flexibility FL increases in linear relationship to aparticular location HT along the hypotube, from the proximal end PR tothe distal end D1, as shown in FIG. 17. Relatedly, a linear flexibilityprofile such as that show in FIG. 17 can be achieved by a hypotubeconfiguration where each hoop has a hoop length 142 that is shorter thanthe hoop length of the neighboring proximal hoop, and each brace has thesame brace length 152. Similarly, hypotubes having a configuration whereeach brace has a brace length that is longer than the brace length ofthe neighboring proximal brace can provide such flexibility profiles.

Optionally, the increasing change in brace length may impart aflexibility profile where the flexibility FL increases in non-linearsmooth and continuous relationship to a particular location HT along thehypotube, from the proximal end PR to the distal end DI, as shown inFIGS. 18 and 19. Relatedly, a non-linear continuous flexibility profilesuch as that show in FIGS. 18 and 19 can be achieve by a hypotubeconfiguration where each hoop has a hoop length 142 that is shorter thanthe hoop length of the neighboring proximal hoop, and each brace has thesame brace length 152, depending on the degree to which hoop lengthdecreases along the hypotube

As noted above, adjacent hypotube hoops 140 can be separated byintervening braces 150. In some embodiments of the invention, each hoophas the same hoop length 142 and each brace has the same brace length152. Such hypotube construction can provide a stiffness or bendingstiffness profile as shown in FIG. 20, where the stiffness or bendingstiffness ST of the hypotube is constant at each location HT along thelength of the hypotube, from the proximal end PR to the distal end DI.Often, flexibility can be inversely related to bending stiffness.Optionally, the hypotube can be constructed so that it provides a firstsection where each hoop has a first hoop length 142 and each brace afirst brace length 152 and a second section where each hoop has a secondhoop length 142 and each brace a second brace length 152, such that thefirst and second hoop lengths are different and the first and secondbrace lengths are different. A hypotube having this configuration canprovide a flexibility profile as shown in FIG. 21, where the stiffnessST of the hypotube increases as a discontinuous stepwise function atlocations HT along the length of the hypotube, from the distal end DI tothe proximal end PR. Spiral hypotubes having discrete stepped pitchregions, such as those shown in FIG. 9B, can also provide such astiffness profile. Similarly, hypotubes having discrete stepped cutwidth regions can provide such stiffness profiles.

In another embodiment, each hoop has the same hoop length 142, and eachbrace has a brace length 152 that is longer than the brace length of theneighboring proximal brace. Hypotube configurations such as this canprovide a stiffness profile as shown in FIG. 22, 23, or 24 depending onthe degree to which brace length increases along the hypotube. Forexample, the increasing change in brace length may impart a stiffnessprofile where the stiffness ST decreases in linear relationship to aparticular location HT along the hypotube, from the proximal end PR tothe distal end DI, as shown in FIG. 22. Relatedly, a linear stiffnessprofile such as that show in FIG. 22 can be achieved by a hypotubeconfiguration where each hoop has a hoop length 142 that is shorter thanthe hoop length of the neighboring proximal hoop, and each brace has thesame brace length 152. Similarly, hypotubes having a configuration whereeach brace has a brace length that is longer than the brace length ofthe neighboring proximal brace can provide such stiffness profiles. Insome cases, a linear stiffness profile such as that shown in FIG. 22 canbe achieved by a hypotube having a constant stiffness profile incombination with a mandrel with a variable stiffness profile, or ahypotube having a constant stiffness profile in combination with one ormore adhesive plugs that provide an overall variable stiffness profile.

Optionally, the increasing change in brace length may impart a stiffnessprofile where the stiffness ST decreases in non-linear smooth andcontinuous relationship to a particular location HT along the hypotube,from the proximal end PR to the distal end DI, as shown in FIGS. 23 and24. Relatedly, a non-linear continuous stiffness profile such as thatshow in FIGS. 18 and 19 can be achieve by a hypotube configuration whereeach hoop has a hoop length 142 that is shorter than the hoop length ofthe neighboring proximal hoop, and each brace has the same brace length152, depending on the degree to which hoop length decreases along thehypotube.

In some cases, the overall stiffness or flexibility profile of theguidewire is a composite profile that collectively reflects theindividual stiffness or flexibility of the components parts of theguidewire, such as a hypotube, a mandrel, and an adhesive plug. Theflexibility and stiffness profiles of the composite structure, or of anyof the individual components or combinations thereof, can mirror or besimilar to any of those profiles shown in FIGS. 15-24.

In some embodiments, bending stiffness can be defined as the slope ofthe force/deflection curve pursuant to a flexural test such as ASTM D790(e.g. 3 point bend test with 1 inch span length). In one testingexample, the distance between two idler wheels center to center, orbetween two contact or fulcrum points, is P. The force measurement wheelor central contact or fulcrum point is centrally disposed equidistantfrom each of the two idler wheels. The deflection distance of the forcemeasurement wheel, or at the center contact or fulcrum point, is 0.200″.Embodiments of the present invention provide guidewires having a bendingstiffness of about 0.04 grams at or near a proximal end where thehypotube is not slotted, 0.008 grams at or near a location about 15 cmfrom the distal end of the hypotube, and 0.004 grams at or near alocation about 1 cm from the distal end of the hypotube. These forcevalues correspond to a deflection distance of 0.200″ in a one inch span3 point bend test. Thus, stiffness can be characterized by the amount offorce required to deflect a tip or section of a guidewire a givendistance off of a known or linear path. Often, flexibility can beinversely related to stiffness. Still further, embodiments of thepresent invention encompass guidewires having a bending stiffness withina range from about 1 gram to about 0.01 grams at or near a proximal endwhere the hypotube is not slotted, where the stiffness force correspondsto a deflection distance of 0.200″ in a one inch span 3 point bend test.Embodiments also encompass guidewires having a bending stiffness withina range from about 0.1 grams to about 0.001 grams at or near a locationabout 15 cm from the distal end of the hypotube, where the stiffnessforce corresponds to a deflection distance of 0.200″ in a one inch span3 point bend test. Embodiments also encompass guidewires having abending stiffness within a range from about 0.05 grams to about 0.0001grams at or near a location about 1 cm from the distal end of thehypotube, where the stiffness force corresponds to a deflection distanceof 0.200″ in a one inch span 3 point bend test.

In some embodiments, tip bending stiffness can be defined as the amountof longitudinal force applied to a distal section of the guidewire, orcomponent thereof, required to deflect or bow that section of theguidewire from a linear alignment. An exemplary testing apparatusincludes a flat surface or force plate coupled with a force gauge, and aclamp or holding device. The distal tip of the guidewire is contactedwith the flat surface, so that the guidewire substantially perpendicularto the flat surface. The holding device is then coupled with theguidewire at a location proximal to the distal tip. The distance betweenthe force plate and the holding device is the deflection distance. Forexample, the holding device can be coupled with the guidewire at about1.2 cm from the distal tip in some tests. In some cases, the holdingdevice can lie coupled with the guidewire at about 2.0 cm from thedistal tip. A longitudinal compression force is then applied to thesection of the guidewire disposed between the flat surface and theholding device, and the force is increased until that section of theguidewire bends, bows, or otherwise deviates from a linear alignment.The amount of force measured at the time the guidewire bends thusreflects the tip bending stiffness. The results of series of exemplarytip bending stiffness tests involving embodiments of the presentinvention compared with a commercial mechanical guidewire are shown inTable 1. Embodiments 1-4 include optical fibers (number, diameter) andmandrel cores (diameter).

TABLE 1 Deflection Deflection Device Distance 1.2 cm Distance 2.0 cmCommercial Device   6 grams   3 grams Embodiment 1 8-45 micron   3 grams1.2 grams fibers .002 flattened core Embodiment 2 8-45 micron 3.5 grams1.6 grams fibers .0025 flattened core Embodiment 3 7-50 micron 3.7 grams1.5 grams fibers .002 flattened core Embodiment 4 7-50 micron 4.1 grams1.6 grams fibers .0025 flattened core

As shown in Table 1, Embodiment 1 includes 8 45 micron fibers and has alower tip bending stiffness than Embodiment 3 which includes 7 50 micronfibers. Thus, a greater number of smaller fibers is more flexible than asmaller number of larger fibers, and the cumulative cross section of thesmaller fibers (8*45=360) is larger than the cumulative cross section ofthe larger fibers (7*50=350). Even though Embodiment 1 has more fibersthan Embodiment 3, it is less stiff than Embodiment 3. The data alsoshows that a larger core mandrel can impart a greater amount ofstiffness. In some embodiments, a guidewire according to the presentinvention can have a distal tip bending stiffness within a range fromabout 3 grams to about 4 grams at a deflection distance of about 1.2 cm.In some embodiments, a guidewire can have a tip bending stiffness withina range from about 2 grams to about 5 grams at a deflection distance ofabout 1.2 cm. In related embodiments, a guidewire can have a tip bendingstiffness within a range from about 1 gram to about 6 grams at adeflection distance of about 1.2 cm. In some embodiments, a guidewirecan have a tip bending stiffness within a range from about 0.5 gram toabout 8 grams at a deflection distance of about 1.2 cm. In someembodiments, a guidewire according to the present invention can have adistal tip bending stiffness within a range from about 1 gram to about 2grams at a deflection distance of about 2 cm. In some embodiments, aguidewire can have a tip bending stiffness within a range from about0.75 grams to about 2.25 grams at a deflection distance of about 2 cm.In related embodiments, a guidewire can have a tip bending stiffnesswithin a range from about 0.5 grams to about 2.5 grams at a deflectiondistance of about 2 cm. In some embodiments, a guidewire can have a tipbending stiffness within a range from about 0.25 gram to about 5 gramsat a deflection distance of about 2 cm.

In some embodiments, guidewires according to the present inventionprovide torque response characteristics similar to other commerciallyavailable mechanical guidewires which do not include hypotubes withvariable stiffness characteristics, which include hypotubes with agreater mass than exemplary hypotube embodiments disclosed herein, orwhich include unslotted hypotubes. In a series of exemplary torqueperformance tests, it was observed that some embodiments of the presentinvention and other commercially available guidewires had a torqueefficiency rating of about 80%. A torque efficiency rating can bedefined as the amount of output rotation at the distal end of aguidewire divided by the amount of input rotation at the proximal end ofthe guidewire. For example, if the proximal end of the guidewire isrotated 360 degrees, and the distal end of the guidewire is observed torotate 288 degrees, then the calculated torque efficiency rating is(288/360=0.80) or 80%. In some cases, guidewire embodiments of thepresent invention were observed to have torque efficiency ratings withina range from about 70% to about 100%.

While the present invention has been particularly shown and describedwith reference to the foregoing preferred and alternative embodiments,it should be understood by those skilled in the art that variousalternatives to the embodiments of the invention described herein may beemployed in practicing the invention without departing from the spiritand scope of the invention as defined in the following claims. It isintended that the following claims define the scope of the invention andthat the method and apparatus within the scope of these claims and theirequivalents be covered thereby. This description of the invention shouldbe understood to include all novel and non-obvious combinations ofelements described herein, and claims may be presented in this or alater application to any novel and non-obvious combination of theseelements. The foregoing embodiments are illustrative, and no singlefeature or element is essential to all possible combinations that may beclaimed in this or a later application. Where the claims recite “a” or“a first” element of the equivalent thereof, such claims should beunderstood to include incorporation of one or more such elements,neither requiring nor excluding two or more such elements.

What is claimed is:
 1. An optical guidewire, comprising: a hypotubecomprising a proximal end, a distal end and at least one segmentdisposed between the proximal end and the distal end; at least one plugarranged within a segment of the hypotube; and a plurality of opticalfibers disposed within the hypotube, wherein each of the plurality ofoptical fibers has a portion extending into a portion of the plug,wherein the plug surrounds at least a portion of the plurality ofoptical fibers and couples the plurality of optical fibers to the atleast one segment of the hypotube, wherein the at least one segment ofthe hypotube comprises an outer surface having a plurality of openings,wherein the outer surface comprises a first series of hoops and bracesand a second series of hoops and braces, wherein the first series ofhoops and braces and the second series of hoops and braces each compriseat least two circumferentially oriented hoops and at least twolongitudinally oriented braces, wherein the at least two braces arecoupled to the at least two hoops, wherein each of the braces has abrace length, wherein the brace length of the first series of braces islonger than the brace length of the second series of braces, wherein thehypotube has a flexibility, wherein the flexibility increases from theproximal end to the distal end.
 2. The optical guidewire of claim 1,wherein each of the hoops has a hoop length, wherein the hoop length ofthe first series of hoops is the same as the hoop length of the secondseries of hoops.
 3. The optical guidewire of claim 1, wherein theflexibility increases linearly from the proximal end to the distal end.4. The optical guidewire of claim 1, wherein the flexibility increasesnon-linearly from the proximal end to the distal end.
 5. The opticalguidewire of claim 4, wherein the flexibility increases non-linearly ata greater profile toward the proximal end of the hypotube.
 6. Theoptical guidewire of claim 4, wherein the flexibility increasesnon-linearly at a greater profile toward the distal end of the hypotube.7. An optical guidewire, comprising: a hypotube comprising a proximalend, a distal end and at least one segment disposed between the proximalend and the distal end; at least one plug arranged within a segment ofthe hypotube; and a plurality of optical fibers disposed within thehypotube, wherein each of the plurality of optical fibers has a portionextending into a portion of the plug, wherein the plug surrounds atleast a portion of the plurality of optical fibers and couples theplurality of optical fibers to the at least one segment of the hypotube,wherein the at least one segment of the hypotube comprises an outersurface having a plurality of openings, wherein the outer surfacecomprises a first series of hoops and braces and a second series ofhoops and braces, wherein the first series of hoops and braces and thesecond series of hoops and braces each comprise at least twocircumferentially oriented hoops and at least two longitudinallyoriented braces, wherein the at least two braces are coupled to the atleast two hoops, wherein each of the hoops has a hoop length, whereinthe hoop length of the first series of hoops is shorter than the hooplength of the second series of hoops, wherein the hypotube has aflexibility, wherein the flexibility increases from the proximal end tothe distal end.
 8. The optical guidewire of claim 7, wherein each of thebraces has a brace length, wherein the brace length of the first seriesof braces is the same as the brace length of the second series ofbraces.
 9. The optical guidewire of claim 7, wherein the flexibilityincreases linearly from the proximal end to the distal end.
 10. Theoptical guidewire of claim 7, wherein the flexibility increasesnon-linearly from the proximal end to the distal end.
 11. The opticalguidewire of claim 10, wherein the flexibility increases non-linearly ata greater profile toward the proximal end of the hypotube.
 12. Theoptical guidewire of claim 10, wherein the flexibility increasesnon-linearly at a greater profile toward the distal end of the hypotube.